Fly fishing
In Scots parlance, the word 'fly' can also mean 'sneaky'. Hence a fly cup is a cup of tea imbibed while working or on duty. And doing something on the fly is not, as in standard English, doing something while in motion or in operation, but doing it without anyone knowing about it.

So fly fishing always makes me smile, as it suggests poaching.

Edit@HLT - I thought the sex might have been taken as read, but I needed to make sure!

*plumps cushions*
( K2k6 has a proper job these days, Mon 29 Sep 2008, 11:43, Reply)